The present invention relates to a method for fabricating superconductive bodies, and in particular to a method for fabricating high temperature oxide superconducting materials.
A superconducting material (La, Ba).sub.2 CuO.sub.4 having a K.sub.2 NiF.sub.4 type structure, which Bednorz and Muller have discovered in 1986, has shown a critical temperature as high as 30K. In 1987, it has been found that YBa.sub.2 Cu.sub.3 O.sub.7-x having a perovskite type structure has a still higher critical temperature T.sub.c =90K and it has shown the superconductive state even at the liquid nitrogen temperature.
By a prior art fabrication method, as disclosed in Japanese Journal of Applied Physics, Vol. 26, No. 5 (1987) pp. L676-L677, e.g. in the case of the Y-Ba-Cu-O oxide superconductive body, powders of Y.sub.2 O.sub.3, BaCO.sub.3 and CuO were mixed at a suitable ratio and calcited in the atmosphere or in a oxygen gas medium at a temperature of 950.degree. C. for one hour. Thereafter, it was shaped in a suitable form such as pellets, etc. and sintered in the atmosphere or in an oxygen at a temperature of 900.degree. C. for about 18-19 hours by means of an electric furnace 9, as indicated in FIG. 2, in which a reference numeral 1 represents a high temperature superconductive body obtained by sintering a pellet made of the superconducting material 10 having the composition described above and 2 indicates a substrate.
The prior art technique stated above had problems that fabrication took a long time, that no attention was paid to mixing of impurities, etc., that productivity and stability were unsatisfactory, etc.
The present invention relates to superconducting materials used for high output magnets, Josephson devices, SQUID, etc. and in particular also to a method for fabricating oxide superconductive thin films working at temperatures higher than the boiling point of liquid nitrogen.
A representative method for fabricating superconductive thin film is published in Japanese J. of Appl. Phys., Vol. 26, No. 5 (1987) pp. L709-L710.
Since the crystal structure of the thin films fabricated by the prior art techniques is complicated and on the other hand fabrication thereof is inevitable for electronic devices, there was a problem that it was difficult to obtain thin films of high quality.